Previously, those organizations wishing to conduct a confidential meeting, secure from being overheard by unauthorized persons, were faced with a difficult and expensive problem. One solution was to locate a facility that had been specifically designed for the purpose. For complete security, however, the facility would have to be checked just prior to each meeting to make sure that all the various means to detect attempts at bugging and otherwise thwart eavesdroppers were operational, had been applied, and had not themselves been compromised.
Alternatively, the meeting could be held in an unsecure room in which provisions had been made for the presence of loud masking audible signals, such as running water or pseudo-random noise, to thwart eavesdroppers.
The cost and inconvenience of these methods made it expensive to conduct secure meetings, and only groups having access to such facilities could conduct such meetings. However, there are many government and private organizations that have the need for such confidentality, and the current invention addresses those needs.
Accordingly, it is the object of the present invention to provide a system that groups can use to conduct secure meetings at any convenient location, such as an ordinary business office or hotel room. The system is highly effective in defeating unauthorized listeners, and yet is small and portable enough to be quickly and easily set up. Power can be provided by a universal power supply that automatically adapts to power standards anywhere in the world. Hand-held speech masks (similar to those used by court stenographers) are used by participants when speaking. These masks cover a speaker's nose and mouth and effectively muffle a speaker's voice to those in the room not electrically connected to the system, such as those attempting to overhear the conversation.
Speech masks have small, integral microphones to carry the signal of each speaker's voice to a summing point in the system, and hence to all the participants. Thus, any number of participants, some or all of whom may be speaking at the moment, can be clearly heard by all other participants through their own headphones. Further, each participant has his own volume control and visual indicator. These visual indicators are driven by the signal from each participant's microphone, thus showing which participant(s) are speaking at an moment. Because direct sound from speakers' mouths is muffled, this feature allows participants to discern who is speaking in case the voice is unfamiliar.
An audio output means is provided so that the proceedings can be recorded by a miniature speech recorder for later transcription.
All of these capabilities are provided in master control unit. In addition, provision is made for the connection of additional slave control units, so that a greater number of participants can be accommodated.
Even though any speech that escapes from a speaker's mask is muffled and difficult to understand, means are provided to mask any such spurious sound, or alternatively to alert the paticipants that speech is escaping from one of the masks so that they will take corrective action. The masking means can be implemented either by the emission of a continuous pseudo-random masking signal on an associated loudspeaker, or by using pressure sensors on the mask to detect imperfect contact with the user's face, thereby sensing the fact that sound may be escaping from a participant's mask and then emit or strengthen the masking sound accordingly. The alerting means can be implemented by using a visual or audible annunciator triggered by the system when it senses that speech may be escaping.
The objects and advantages of the present invention will be clearly understood from the following description, taken in conjunction with the drawings.